1.INDIVIDUALISTICALLY RATIONAL (IR) = to Maximize One's Expected Return
(Total Expected Benefits Less Total Expected Costs).This sense of rationality is the
twentieth-century development of the concept of INSTRUMENTAL RATIONALITY.It is the notion of rationality that is
employed in economics.(Note that to be
INDIVIDUALISTICALLY RATIONAL does not require that one be an egoist.)

2.COLLECTIVE
ACTION PROBLEM = A situation in which everyone (in a given group) has a choice
between two alternatives and where, if everyone involved chooses the
alternative act that is Individualistically Rational (IR), the outcome will be
worse for everyone involved, in their own estimation, than it would be if they
were all to choose the other alternative (i.e., than it would be if they were
all to choose the alternative that is not IR).

By convention, in any Collective Action Problem, the IR
alternative is referred to as "Defection" ("D"); and the
non-IR alternative is referred to as "Cooperation" ("C").

II.Hobbes's State Of Nature Is A Collective
Action Problem

Everyone else

Make Peace

(C)

Make War

(D)

Make Peace

(C)

+100,

+100

-110,

-99

Make War

(D)

+110,

+95

-100,

-100

N-Person Prisoners' Dilemma:A Collective Action Problem Involving

A Decision to Cooperate (C) or Defect (D).

FREERIDING.In a Collective Action Problem in which most
agents choose to Cooperate, Defectors are referred to as FREERIDERS, because
they benefit from the Cooperation of others, but are unwilling to reciprocate
Cooperation.